In order to efficiently transport electricity, conductors are energized at high voltage. Conductors, generally manufactured of conductive metal, are configured into a plurality of wires, commonly referred to in the art as cables. More specifically, in the case of an electric cable carrying electricity from an electrical substation to the vicinity of an end user, the cables—designed to operate up to 35,000 volts under standard conditions—are referred to as distribution cables. In many applications, it is necessary to insulate (i.e., cover the conductor with an electrically insulating material) cables with a partially or fully insulating material.
The primary purpose of splicing is simply to allow for cabling to be sectionalized (i.e., breaking up the lengths of cable into easily pulled sections). In order to allow for uninterrupted service, fault protection, and maintenance, cables must be spliced and joined. The need for high-voltage cable splicing may also arise due to additional cable connection requirements resulting from residential expansion and increasing energy demands. The disconnectable joints, which can mate up to four cables at one junction, need to functionally mate the conductor, insulation, and insulation shield in a manner to allow for the connected cables to operate as one continuous cable. Unlike the splicing of low-voltage devices, which may be accomplished with the use of simple connectors with minimal insulation (frequently constructed of copper, aluminum and like components), high-voltage devices require splices which must maintain proper voltage grading, electrical insulation, and water tightness. To achieve these requirements, premolded high-voltage splices may include the use of one, two, three, or more insulated members. In addition, a tight fitting rubber member or sleeve may also be employed to cover the cable member connections. Due to the fact that the sleeve is generally manufactured of one diameter, cable adapters may be employed to accommodate a broad range of cable diameters. Therefore, in combination, the insulated members, sleeves and cable adapters secure the spliced region, thereby providing for protection against water seepage into the connection. In addition, this type of assembly allows the cable-to-cable splice to achieve the desired voltage and insulation demands. Such a fitting requires a careful and often timely installation process, which involves the connection of opposing cable members to, and/or the placement of cable adapters over, the cable insulation. Cable adapters or cable members are then connected to one another, or to other connector components, to provide a successful splice. Specifically, installation involves the cables being bolted onto the central bus and the sleeves being slid over the cable insulating and mating with the central bus' insulation. It is further known in the art to require additional components to be installed on-site for securing opposing cable adapters or cable members to one another. As a result, as the number of additional installation components increases, more assembly time may be required in the field, which can alter the efficiency of the splicing operation.
For a successful splice, the cable members must fit securely within the corresponding splice components. The inside diameter of the splice component is generally designed to be smaller than the outer diameter of each corresponding cable member (i.e., commonly referred to as the “interference fit”). To insure a snug fit, lubricant may be applied along the outside of the cable members and/or the inside of the cable adapters to assist in the installation process as the cable adapters are pulled over the corresponding cable members.
Cable joints are designed to be disconnected and reconnected without damaging the joint. Typically, such joints are designed such that the joint conductor is manufactured of a solid metal “bus” with flat pads at the terminals. The flat pad connector is mounted onto the cable in a manner designed to be mated to the flat pad of the joint to ensure an effective electrical connection. To complete the joint, the bus is covered with an electrical insulating material and the insulating material is covered with a partially or fully conductive shield. Once the connection is established, it is necessary to restore the continuity of the insulation and insulation shield by using an elastomeric multi-layer sleeve to bridge the cable insulation and shield to the joint insulation and shield.
In order to restore the continuity at the joint while shielding the joint from the elements common in power systems, shields, commonly referred to as sleeves, are designed to provide an interference fit and incorporate heat-shrink characteristics or cold-shrink characteristics to ensure a snug and water-tight joint. For example, a multi-layered sleeve can have an interference fit over the cable and the joint. As mentioned, the inside diameters of the ends of the sleeve are smaller than the outside dimensions of the cable insulation at a first end and smaller than the joint insulation at the second end. The interference fit allows for a continuous insulation covering and provides for a leak-proof submersible design between the cables at the joint. While interference fit designs accomplish the desired objectives in the field, such designs require the addition of cable adapters for mating to cables of various sizes. While the use of additional components is tolerated in the field since cable adapters are necessary to complete a secure splice, it is not ideal in the field as high voltage components often reside in confined spaces underground and the installation proves difficult. Specifically, it is cumbersome to force fit the sleeve over the cable adapter and the joint without dislodging the location of the adapter, thereby compromising the splice. Furthermore, the use of cable adapters creates additional interferences which may result in additional points of fault thereby jeopardizing the integrity of the splice.
Heat-shrink sleeves are manufactured of material which remains at an expanded size and shape at common environment temperatures and conditions. When sufficient heat is applied, the sleeve “shrinks” to form a secure fit between cable insulation/shield to joint insulation/shield. Once reduced to a shrunken state, the elasticity of the material utilized allows for the sleeve to remain at such state with minimal expansion through a wide range of environmental conditions. While this is a common method utilized in the art, several disadvantages are experienced in the field during assembly. For example, the thickness of elastomeric sleeves makes it difficult for a lineman to apply consistent and uniform heat in the confined space common to joint assembly in a high voltage environment. Such difficulty in the field often results in scorching and deformation of the sleeve, rendering the sleeve ineffective in providing a water-resistant secure splice. Furthermore, since consistent and high temperature heat is required, a safety concern is apparent.
In the case of the cold-shrink sleeves, a sleeve is pre-stretched and maintained in an expanded state by using a rigid core inserted therein. The cold-shrink sleeve shrinks to fit tightly over the cable insulation and the joint insulation upon physical removal of the rigid core. Again, while cold-shrink designs accomplish the desired objectives in the field, currently available cold-shrink sleeves known in the art are designed to cold shrink along the entire length of the sleeve, which in current practice is generally greater than twelve inches, and the increased dimension of the sleeve requires a removable core of equal or greater length. As mentioned, components of such length prove difficult to assemble in the confined space common to joint assembly in a high voltage environment and failure of the proper removal of the core may result in complete failure of the joint requiring reinstallation. Further, once installed, the joint is no longer disconnectable, since it is not possible to disassemble the joint without cutting off the sleeve.
Since the methods discussed herein have been employed in the art for decades, numerous disclosures are known in the art that employ the interference fit, heat-shrink characteristics, or cold-shrink characteristics splicing apparatus and methods discussed above. For example, Fallot U.S. Pat. No. 3,980,374, entitled “Separable splice connector,” teaches of a separable splice connector for use with 15 to 25 kilovolts and 600 amperes of current. The connector employs a unitary splice body assembly. The splice body assembly is constructed of molded elastic material and may be utilized for providing a straight splice.
A second apparatus comprising a pre-molded high voltage splice is disclosed in Lien U.S. Pat. No. 5,041,027, entitled “Cable splice.” Lien discloses a system for electrically connecting a first power cable end to a second power cable end. The splice system comprises a first probe adapted to be electrically connected to the first power cable end and a second probe adapted to be electrically connected to the second power cable end and a cable splice. The cable splice further comprises two ends wherein a first female contact assembly is adapted to engage with the first probe and a second female contact assembly is adapted to engage with the second probe thereby forming a splice.
In a further example, Yaworski U.S. Pat. No. 7,901,243, entitled “Methods and systems for forming a protected disconnectable joint assembly,” teaches of a method for forming a protected disconnectable joint assembly using a disconnectable joint assembly wherein the disconnectable coupling mechanism is selectively operable to disconnect the cable connector from the busbar by severing the sleeve, but without severing the secured cable. In short, Yaworksi discloses a cold-shrink sleeve with the cold-shrink portion being on the joint end. The method for assembling the joint assembly includes the use of “an electrical transmission power cable including a conductor and a cable insulation layer covering the conductor, the conductor having a terminal end; an electrically conductive cable connector affixed to the terminal end of the power cable and having a connector coupling portion; a busbar including an electrically conductive busbar body, a busbar coupling portion extending from the busbar body, and a busbar insulation layer covering the busbar body; and a disconnectable coupling mechanism mechanically securing the cable coupling portion to the busbar coupling portion to provide a joint between the cable and the busbar.” The Yaworski method requires “maintaining the joint cover assembly in an expanded state using a removable holdout device mounted within the sleeve body; mounting the joint cover assembly on the holdout over the joint between the cable and the busbar; and thereafter removing the holdout device from the joint cover assembly to release the sleeve body to contract onto the disconnectable joint assembly such that the sleeve body circumferentially surrounds the joint between the cable and the busbar, overlaps portions of the cable insulation layer and the busbar insulation layer adjacent the joint, and applies a persistent radially compressive load on the cable insulation layer and the busbar insulation layer.”
Numerous other splicing mechanisms employing the referenced apparatus and methods are known and utilized in the art. However, none of the currently employed systems provide for an effective splice utilizing a combination of cold-shrink and interference fit splice components. Current inefficient design tends to make the performance of this type of splicing unduly time-consuming, resulting in increased labor, time, and cost.
Thus, there exists a need for an invention which resolves the limitations of the prior art by providing a suitable means for completing a field splice of common high voltage components employing a combination of cold-shrink and interference fit in a single splice component. The single device of the present invention allows for the use of a shortened core at a first cold splice end and absence of a cable adapter at the interference fit second end.
While aforementioned methods and apparatuses are generally suitable for the particular purpose discussed herein, it is clear that there exists a need in the art for an improved method and apparatus that progresses the state of the art, as well as one that provides the additional benefits enumerated in the present application.